In Joseph Conrad's Heart of Darkness, Marlow's respect toward the natives is found in the empathy he has for the way they are treated, and his efforts to protect them.
The Congo has been taken over as a Belgian colony. Ivory is like gold, and the Belgians want as much as they can get, to fill the demand in Europe. When Marlow arrives at the Lower Station as a steamship captain to bring one agent (Kurtz) from the depth of the jungle, he is confronted with lunacy and waste on the part of the white men running the station: setting off dynamite for no purpose; letting machinery lie around in abandon, rusting and discarded. It is, however, distress over the plight of the enslaved natives—the atrocities carried out against them—that conveys such a strong sense of pain on Marlow's part:
Six black men advanced in a file, toiling up the path...Black rags were wound round their loins...I could see every rib, the joints of their limbs were like knots in a rope; each had an iron collar on his neck...All their meagre breasts panted together, the violently dilated nostrils quivered, the eyes stared stonily uphill. They passed me within six inches, without a glance, with that complete, deathlike indifference of unhappy savages.
Their guard looks at Marlow with a knowing grin, as if accepting him into his world because Marlow is white. Marlow turns away to more natives driven by white "red-eyed devils, that swayed and drove men—men, I tell you...For a moment I stood appalled..."
Traveling down a slope, Marlow is confronted with more living horror:
Black shapes crouched, lay, sat between the trees leaning against the trunks, clinging to the earth, half coming out, half effaced within the dim light, in all the attitudes of pain, abandonment, and despair...this was the place where some of the helpers had withdrawn to die.
They were dying slowly—it was very clear. They were not enemies, they were not criminals, they were nothing earthly now—nothing but black shadows of disease and starvation, lying confusedly in the greenish gloom.
Marlow looks around at the poor souls that are working for the whites against their will. He finds himself close to a seemingly young man. He hands the man a biscuit to eat. Others are lying about...
...scattered in every pose of contorted collapse, as in some picture of massacre or pestilence...I stood horror-struck...
Everywhere Marlow travels, to the Central Station, and then heading to the Inner Station to find Kurtz, he sees all kinds of horrific violence visited upon the natives. Chugging along the river, the pilgrims (agents for the Company) fire their rifles into the jungle with the intent of killing unseen blacks.
At one point, Marlow takes steps to save potential victims of these Company employees:
I pulled the string of the whistle, and I did this because I saw the pilgrims on the deck getting out their rifles with an air of anticipating a jolly lark. At the sudden screech there was a movement of abject terror through that wedged mass of bodies. 'Don't! don't frighten them away,' cried someone on deck disconsolately. I pulled the string time after time.
Marlow does not have experience of the natives of the Congo, but he doesn't need to: he sees them as men—not slaves; not criminals. He sees them as victims. His empathy is palpable. He is offended and horrified for their sakes. He even makes a conscious effort to save those who can still get away.
His attitude defines his respect.